This invention relates to a reciprocating compressor for compressing a gas by the reciprocating movement of a piston and, in particular, to a structure of a suction path for sucking the gas into a cylinder bore.
There are known various types of reciprocating compressors such as a fixed displacement compressor comprising a swash plate having a fixed inclination angle, a variable displacement compressor comprising a swash plate having a variable inclination angle, and so on. Each of these compressors comprises a cylinder block having a plurality of cylinder bores extending in a predetermined direction, a plurality of pistons inserted into the cylinder bores, respectively, a cylinder head disposed at one end of the cylinder block in the predetermined direction, and a valve plate assembly interposed between the cylinder block and the cylinder head.
The valve plate assembly comprises a valve plate with a plurality of discharge valves and a plurality of suction valves fixed to opposite surfaces thereof. The valve plate has a plurality of discharge ports and a plurality of suction ports corresponding to the cylinder bores, respectively. Each of the discharge valves and the suction valves is a leaf valve having a fixed end and a free end in the manner known in the art. The discharge valves and the suction valves are attached to the valve plate to close the discharge ports and the suction ports, respectively. Following the reciprocating movement of the pistons, the discharge valves and the suction valves open and close the discharge ports and the suction ports, respectively. The cylinder block is provided with a plurality of stoppers each of which is engaged with the free end of each of the suction valves to limit a maximum bending of the suction valve (for example, see Japanese Examined Utility Model Publications (Y) No. H03-35899 and S53-32881).
Each of the suction valves is operated in the following manner. When no load is applied, the suction valve is substantially brought into contact with the valve plate. When the piston is moved away from the valve plate, a bore pressure within the cylinder bore is lowered. In this event, if the sum of the bore pressure acting upon the suction valve, a bending stress of the suction valve, and a viscous force of a lubricating oil between the suction valve and the valve plate becomes lower than an internal pressure of the cylinder head, the free end of the suction valve is separated or released from the valve plate to be opened. On the other hand, when the piston is moved towards the valve plate, the bore pressure is elevated. In this event, if the above-mentioned sum becomes higher than the internal pressure of the cylinder head, the free end of the suction valve is brought into contact with the valve plate to be closed.
In the above-mentioned structure, an open timing of the suction valve is delayed due to the bending stress of the suction valve and the viscous force of the lubricating oil between the suction valve and the valve plate. Accordingly, simultaneously with the suction valve""s opening after delay, a refrigerant is abruptly sucked because the bore pressure is considerably decreased at that time instant. This results in an increase in pulsation of suction flow. If a cooling load within a car compartment is reduced so that a sucking amount of the refrigerant is reduced, the bending of the suction valve is reduced so that the free end of the suction valve can not be brought into contact with the stopper. In this event, self-induced vibration is caused in the suction valve. This results in an increase in pulsation of suction flow and in generation of a noise.
It is therefore an object of this invention to provide a reciprocating compressor in which pulsation of suction flow of a refrigerant can be reduced effectively and without inducing other vibration and which can be produced at a reduced cost.
Other objects of this invention will become clear as the description proceeds.
According to an aspect of this invention, there is provided a reciprocating compressor which comprises a cylinder block having a cylinder bore, a piston inserted into the cylinder bore to perform reciprocating movement, a valve plate coupled to the cylinder block and having a suction port communicated with the cylinder bore, and a suction valve of a leaf valve placed between the valve plate and the cylinder block for opening and closing the suction port in response to the reciprocating movement of the piston. In the reciprocating compressor, the suction valve is previously bent to open the suction port in an initial state when the compressor is stopped.
According to another aspect of this invention, there is provided a reciprocating compressor which comprises a cylinder block having a plurality of cylinder bores, a plurality of pistons inserted into the cylinder bores to perform reciprocating movements, respectively, a valve plate coupled to the cylinder block and having a plurality of suction ports communicated with the cylinder bores, respectively, and a plurality of suction valves of leaf valves placed between the valve plate and the cylinder block for opening and closing the suction ports in response to the reciprocating movements of the pistons, respectively. In the reciprocating compressor, the suction valves are previously bent towards the stoppers to open the suction ports, respectively, in an initial state when the compressor is stopped. The pistons perform the reciprocating movements with a predetermined phase difference from one another.